18/410 Neck: the Dropper and Sample Standard
By Joe Joo · 8PCK · Shantou · Updated 26 October 2026
18/410 is the smallest standard neck in cosmetics: droppers, sample serums and small applicators. It is also the one most often mismatched with 18/415.
18/410 is a diameter of 18 mm with a 410 thread. It is the default for 10–30 ml droppers and small applicators, because the closure is small enough to look proportionate on a sample.
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What Fits An 18/410
Droppers, small screw caps, applicators and some sprayers. The 18 mm diameter keeps the pack visually small.
Dropper
The most common closure: 10–30 ml serums and oils.
Screw Cap
Refill and sample caps; costs less than a dropper.
18/410 Vs 18/415
Both are 18 mm; the thread height differs. A 410 closure threads onto a 415 neck and leaks. Ask for the thread code on the drawing.
Where It Fails
A dropper tube that is too short leaves the last millilitre unusable — at 10 ml that is 10 % of the fill.
How to Confirm the Neck Before Ordering
The 18/410 code is a diameter plus a thread profile, and both have to match for droppers and samples.
Measure T, E and H
T is thread height, E is the gap between threads, H is the height to the sealing surface.
Send the Closure
A pump that fits a drawing can leak on a bottle. Test the pair, not the part.
Check the Drawing, Not the Photo
Two bottles can look identical and differ by 5 mm of thread.
What to Send in a Brief
Neck (18/410), bottle capacity, closure model and quantity. With those four we confirm fit before quoting.
Questions We Get on This
What is an 18/410 neck used for?
Dropper bottles, sample serums, oils and small applicators, usually 10–30 ml.
Will an 18/410 cap fit an 18/415 bottle?
It threads on but does not seal. The thread height differs.
What closures are available?
Droppers (bulb or push-button), screw caps and small applicators.
What is the MOQ?
1,000 pcs per colour.
What does 18/410 mean?
Diameter in millimetres plus the 410 thread profile — the second number is not a diameter.
Can I mix 410 and 415?
No; they thread together and leak. Confirm the code on the drawing.
Do you test the closure?
Yes, on the filled bottle before packing.
Sizes That Fit This Guide
Get a Price on This, Within One Business Day
Tell us the capacity, the neck and the quantity. You get unit price, lead time and a sample plan — not a catalogue.
Every batch is gauged at the neck and weighed. The documents travel with the shipment.